For the first time German petty patent DE-GM 77 12 901 discloses a locking nail which is used for the osteosynthesis. The locking nail is driven distally or proximally into the hollow bone after preparing the bone cavity. Using conventional nails, the bone cavity is often enlarged by drilling. The ends of the nail are provided with cross bores to receive cortical screws to fix the locking nail in both the axial and rotational direction. This effectively stabilizes the fracture.
The known locking nail is axially slotted which is a drawback when the nail is subjected to a torsion when being driven in, so that bony material is damaged. Therefore, European patent 118 778 disclosed a circular closure of the hollow nail shaft and a trefoiled or starlike profile, for example.
For mounting the cortical screws it is necessary to drill the corticalis in alignment with the cross bores of the nail. There are known numerous positioning means to find the cross bores in the nail and to drill the bores in the corticalis. A number of positioning means use X-rays and a monitor. Other positioning means cooperate with the driving-in end of the nail. The distance of the cross bores from the nail end is known; accordingly this determines the position of the cross bores in the bone. Since, however, the known locking nails are mounted by exerting substantial forces, the nail shaft may twist or bend so that the expected position of the cross bore deviates from the actual position.
Up to now the locking nails have been primarily used for leg bones, wherein a special shape and dimension of the nail shafts have been provided for the femur and the tibia. In particular the shafts have been subjected to a curvature corresponding to the bone shape. It is of course expensive to store a variety of locking nails to be used for different bones.
It is an object of the present invention to provide a locking nail which is used as a standard nail for plurality of bone cavities and which is selected with respect to its length only. Furthermore, the bone nail should be suited for a dynamic medical care as well as for subjecting compression and/or distraction forces.
These objects are solved by the locking nail of the invention.